The invention relates to a holding device for molds, mold halves or die holders in an injection molding machine, furthermore a die holder, which can be inserted into this holding device, furthermore an injection molding machine containing this holding device and apart from this a process for the removing, respectively, inserting of a mold, mold half or a die holder in accordance with the generic terms of the independent claims.
Known injection molding machines frequently have the disadvantage of high setting-up or re-tooling times and costs, because the inserting, removing or changing of molds is complicated and time-consuming. The mold, half mold, resp., their holder is after all in the case of the known injection molding machines a part of the machine itself. This means that, in the case of a mold change, a part of the machine itself has to be changed. This is rendered more difficult by the fact that, for the purpose of cooling, hydraulic actuation, etc., various media, such as electric power, water (cold and hot), oil (cold and hot), air and/or other gases are introduced into the injection mold. The corresponding supply and return lines are connected to the mold, i.e., to the mold halves. Therefore, in the case of a mold change, these lines have to be disconnected from the old mold and connected to the new mold. This procedure requires time and work effort. The utilization of conventional injection molding machines is correspondingly expensive and not very flexible, if the molds have to be changed frequently. Modern injection molding plants, however, have to be in a position to change injection molds quickly and easily, in order to be able to immediately adapt their production to changing customer requirements and to other continuously changing demands and conditions.
For many applications of the injection molding process it is advantageous if the injection mold or one mold half can be rotated relative to the injection molding machine. With such a rotatable mold, the possibility exists of injecting the molten mass of plastic material into the mold from several injection stations, which typically are on opposite sides of the mold. With this arrangement, simultaneously molded components with differing geometrical shapes, different colors or ones made of different materials can be manufactured (multicomponent process). Therefore, molded components can be made that have different colors or which are made of several materials (assembly injection molding). If only a single injection station is used, such a rotatable mold provides the benefit of shorter cycle time. This is because, after a first injection cycle, the mold can be rotated and the molded components injected immediately beforehand can cool down and be ejected, while a second injection cycle is already in progress. With rotatable molds more cavities are available than in the case of non-rotatable molds. Apart from this, rotatable molds make intermediate stations for various options possible.
Injection molding machines with rotatable molds or mold halves are known. Thus, for example, U.S. Pat. No. 4,330,257 teaches an injection molding machine with two die holders displaceable relative to one another and a core holder body in between, which has at least four side surfaces and which can be rotated around an axis vertical to the direction of displacement of the mold holder plates. On both mold holder plates there are first mold halves with forming cavities; the side surfaces of the core holder body are equipped with finger-like extrusions and together with these fingers form second mold halves. If the two mold holder plates are pushed against the core holder body, then the first and second mold halves are assembled into molds, into which molten mass is injected from two injecting stations. Injection molded components created by this are removed from the cavities on the fingers,
The patent document DE-36 20 175 divulges an injection molding machine with at least two plastification and injection units and two mold holder plates. One of the mold holder plates is fixed, the other one can be displaced on spars. Between the mold holder plates there is a rotatable and also displaceable prism-shaped core holder body. Located on the mold holder plates are first, on the core holder body, second mold halves of the injection molds. By displacing the displaceable mold holder plate and the core holder body the first and second mold halves are assembled to an injection mold.
In the case of such injection molding machines with rotatable molds or mold halves, the disadvantage of the long re-tooling times because of difficult to change molds is particularly clearly noticeable. The molds or mold halves are respectively connected with a rotation mechanism, the distance of which from the molds or mold halves renders the mold change more difficult in addition.
The present invention is directed toward a holding device for a mold, mold half or die holder in an injection molding machine, that significantly reduces setting-up and re-tooling times, and therefore makes possible easy and rapid removal, insertion, and changing of the mold, mold half or the die holder. The present invention is further directed toward a die holder that can be inserted into the aforementioned holding device. Furthermore, the present invention is directed toward an injection molding machine that overcomes the disadvantages of prior art, and which permits short setting-up and re-tooling times are possible. The present invention is further directed toward a method for the easy and rapid removal, insertion, and changing of the mold, mold halves or of the die holder.
The invention breaks with the conventional concept, according to which the injection mold, resp., its holder is a component part of the injection molding machine itself. Instead of this the present invention provides the injection mold, the mold half, resp., its holder as a module, which can be inserted into the injection molding machine and changed as required. For this purpose, a holding device for at least one mold, mold half or a die holder in an injection molding machine is created. This holding device comprises at least two holding devices, which can be displaced relative to one another and possibly rotated, for the releasable clamping of the mold, mold half or the die holder. The holding device, not the mold itself, is a component part of the injection molding machine. On the holding device in accordance with the invention all media lines required are connected permanently. In contrast, different injection molds can be inserted into holding means or holding devices and changed again without any effort. The loss-free transfer of the different media from the holding device to the mold and vice-versa is assured by standardized interfaces.
A preferred embodiment of the holding device in accordance with the invention contains two displacement units. A rotating unit is mounted on each of the displacement units. On each rotating unit there are holding means for molds, mold halves or their holders. The displacement units can be displaced relative to one another in one direction, for example, on two spars respectively parallel to one another. Each rotating unit is rotatably mounted on the respective displacement unit such that it can be displaced with the displacement unit and rotated around an axis displaceable with the displacement unit, which axis is vertical to the direction of displacement. The holding means are affixed to the displacement units in such a way, that they are opposite one another, that their axes coincide and that the holding means have a certain spacing from one another, when the two displacement units are in a certain position relative to one another. In this one certain relative position, in the space between the two holding means a mold, a mold half or a die holder can be reversibly clamped.
The mold, the mold half or the die holder inserted into the holding device according to the invention can be displaced in one direction and possibly rotated around a displaceable axis vertical to the one direction. The displacement of the holding device can be actuated by means of, for example, hydraulic and/or electric driving means, and controlled or regulated with control or regulating means. The rotation of the holding means can, for example, be actuated by means of rotating driving means and can be controlled or regulated with rotation control or rotation regulating means.
A die holder in accordance with the invention is preferably a prism-shaped rotating block, the two base surfaces of which are facing the two holding means. The rotating block has at least two side surfaces, whereby at least one side surface accommodates an injection mold or an injection mold half.
The holding device in accordance with the invention is preferably inserted between two mold holder plates of an injection molding machine. In doing so, in preference one mold holder plate is permanently fixed to the machine while the other mold holder plate can be displaced in the same direction as the displacement units of the holding device. The mold holder plates each accommodate a first mold half. At least one, in preference two or more side surfaces of the prism-shaped block accommodate second mold halves. First and/or second form halves are equipped with forming cavities. When the mold holder plates are pressed against the rotating block, the first and second mold halves are joined together to form injection molds, into which a molten mass can be injected from injection stations.
For the removal of a mold, mold half or of a die holder from the device in accordance with the invention, the holding means are displaced relative to one another to such an extent that they release the mold, mold half or the die holder. Thereupon the mold, mold half or die holder is removed from the holding device.
For inserting a mold, mold half or a die holder into the holding device in accordance with the invention, the holding means are displaced to such an extent that they have a spacing between one another enabling the insertion of the mold, mold half or die holder. The mold, mold half or the die holder is inserted into the holding device. Thereupon, the holding means are displaced relative to one another into the one certain relative position, so that they clamp the mold, mold half or the die holder.
The holding device in accordance with the invention can be built into already existing injection molding machines. It provides both the benefits of the known injection molding machines with rotatable molds as well as the advantage of an easy mold change.